This invention relates to verifying the identities of telephone callers.
Security systems provide protection for credit card owners by reducing the possibility that an unauthorized person will successfully initiate a financial transaction using the card owner's credit card number. For example, the card owner may choose a personal identification code that serves as a password to be used in conjunction with the credit card account. When a caller attempts to initiate a financial transaction over the phone with a mail order company or similar organization, the caller may be asked to provide the personal identification code that is associated with the account. A person receiving the call at the mail order company has access to the valid personal identification code. If the caller provides an incorrect personal identification code, a freeze is placed on the credit card account, and the card holder is notified of the incident.
Similarly, a holder of an automated teller card may choose a personal identification code or a password. When a person inserts the card into an automated teller machine, the machine requests the person to punch the personal identification code or the password into a keypad on the machine. If the personal identification code or password matches the personal identification code or password of record for the bank account, the transaction is allowed to proceed. If the person at the automated teller machine does not punch in the correct personal identification code or password after a given number of attempts, the automated teller machine retains the card and the card holder is notified of the incident.
Voice processors, generally, are devices that receive speech and identify the word being spoken. Speaker verification units, generally, are voice processors that verify whether a particular password is being spoken. Such a device is used in conjunction with a database to which the speaker verification unit is attached. The database stores a set of digitized and "vectorized" passwords. The speaker verification unit digitizes the password being spoken, producing a digitized output, "vectorizes" the digitized output by transforming the digitized output into a vector of voice characteristics, and compares the digitized and vectorized output with a digitized and vectorized password selected from the database. The password being spoken may be received by the speaker verification unit over a telephone line. The speaker verification unit verifies whether the digitized and vectorized output adequately matches the digitized and vectorized password selected from the database. Some speaker verification units are unlikely to verify a match unless the person speaking happens to be a person who earlier spoke the password in order to store the password in the database.
Another type of speaker verification unit verifies whether the person speaking is a particular person, regardless of what the person is saying. The speaker verification unit extracts from the person's speech certain information characteristic of the person's speech. This information is known as the person's "voice print." A voice print is an example of a biometric signal. The speaker verification unit compares the voice print with a voice print selected from the database. The speaker verification unit verifies whether the voice print it has extracted from the person's speech sufficiently matches a voiceprint selected from the database.
One published paper, Takahashi et al., "SR-2000 Voice Processor and Its Applications," NEC Res. & Develop., No. 73, April 1984, describes a bank system or a credit card service system in which speaker verification units are located at each of a set of service areas at differing locations. The speaker verification units are remotely controlled, via data communication lines, by a system controller that is located at a central service area. A customer may call a remote service area and request information relating to a bank account or a credit card account using a service code that identifies the type of information requested, an account number that identifies the customer's account, and an identification number that identifies the customer. When a customer calls a remote service area, the speaker verification unit at that remote service area receives the call and the centrally located system controller accesses customer information from a host computer at the central service area and uses the received information to control the speaker verification unit via a data communication line while the call is in progress.